Steel cables are conventionally used for supporting and/or driving an elevator car in elevator installations. According to a development of such steel cables, belt-like support means comprising tensile carriers and a casing arranged around the tensile carriers are also used. Such belt-like support means are, similarly to conventional steel cables, guided in the elevator installation over drive pulleys and deflecting rollers. However, by contrast to steel cables belt-like support means are not guided as a whole in grooves in the deflecting rollers or drive pulleys, but the belt-like support means lie substantially on the deflecting rollers or drive pulleys.
Support means do not always run in elevator installations exactly perpendicularly to the axis of deflecting rollers or drive pulleys. Occurrence of diagonal tension can be caused on the one hand by a construction or on the other hand by imprecise mounting of the elevator installation. Due to such diagonal tension of the support means there is the risk that the support means slips laterally off a deflecting roller or a drive pulley. In order to prevent this, elevated side edges are used at the deflecting rollers or drive pulleys or also longitudinal ribs and longitudinal grooves in support means as well as on the traction surface of the deflecting rollers or drive pulleys, which interengage and thus ensure lateral guidance.
However, it has proved that measures such as elevated side edges or longitudinal grooves in support means cannot prevent lateral jumping-off of the support means in every instance. Particularly in the case of support means with longitudinal ribs it was observed that the support means due to diagonal tension was laterally displaced by one or more longitudinal ribs so that the support means protruded laterally beyond the deflecting roller without entirely jumping off laterally. There is thus the risk that a support means at least partly laterally jumps off a deflecting roller or a drive pulley without this being recognized by the safety systems of the elevator installation.